1. Field of the Invention
The present invention relates to a developing apparatus used in an image forming apparatus of electrophotographic type or electrostatic type such as a copying machine, a printer and is the like and adapted to develop an electrostatic latent image formed on an image bearing member.
2. Related Background Art
In image forming apparatuses using an electrophotographic process such as printers, a photosensitive drum (image bearing member) is uniformly charged, a latent image is formed on the photosensitive drum by selective exposure to the photosensitive drum, the latent image is visualized by toner (developing agent) as a toner image, and the toner image is transferred onto a recording medium. By applying heat and pressure to the transferred toner image, the toner image is fixed to the recording medium. In this way, image recording is effected.
In such image forming apparatuses, toner replenishment and maintenance of various process means are required. In order to facilitate the toner replenishment and the maintenance, there has been proposed a process cartridge in which the photosensitive drum, a charge means, a developing means and a cleaning means are collectively housed in a cartridge frame.
In such an apparatus, a developing apparatus for visualizing the latent image comprises a developing roller as a means for supplying toner stored in a developing frame to the photosensitive drum, a developing blade for regulating an amount of toner supplied to the developing roller, seal members (made of felt or the like) for preventing leakage of toner toward a longitudinal direction of the developing roller at both ends of an opening of the developing frame, and a sheet member for preventing the toner from escaping through gaps created between a lower part of the developing roller and the opening and the seal members at a lower part of the opening of the developing frame.
The sheet member is attached to the lower part of the opening of the developing frame, and one of width-wise ends is a free end. And, a part of the free end abuts against a peripheral surface of the developing roller along its entire longitudinal (axial direction of the developing roller) area.
On the other hand, longitudinal portions of the sheet member extend to positions where the sheet member overlaps with the seal members, thereby preventing the toner from escaping through the gaps.
FIG. 9 shows an example of a developing apparatus having such end seal members.
Seal members 105 are disposed between a developing roller 102 and a developing frame 101 at both longitudinal sides of a developing blade 103. The seal members 105 are generally made of flexible material formed from felt with fibers and are secured to the developing frame 101.
In order to maintain sealing ability between the seal members 105 and the developing frame 101, end faces 105a of the seal members 105 near a sheet member 106 are urged against a longitudinal rib 101a of the developing frame 101 to which the sheet member 106 is adhered.
However, particularly when the developing roller 102 has a small diameter, it is difficult to closely abut the end faces 105a of the seal members 105 against the longitudinal rib 101a of the developing frame 101, and, thus, a special technique is required for attaching the seal members 105.